Question 1159647: Plastic sheets produced by a machine periodically monitored for possible fluctuations in thickness. If the true variance in thicknesses exceeds 2.25 square milli- meters, there is cause for concern about product quality. Thickness measurements for random sample 10 sheets produced in a particular shift were taken, giving the following results (in millimeters): 226 226 232 227 225 228 225 228 229
a. Find the sample variance.
Found 2 solutions by Boreal, ikleyn:
Answer by Boreal(15235)   (Show Source):
You can put this solution on YOUR website! Put them into the calculator with STAT EDIT and L1
Then use STAT CALC 1 1-Var Stats
the std deviation is 2.236, which is the sqrt 5 (noted)
That squared is the variance, which is 5 mm^2 (note the units)
Answer by ikleyn(52865)  (Show Source):
You can put this solution on YOUR website! .
The post says
Thickness measurements for random sample 10 sheets produced in a particular shift were taken,
giving the following results (in millimeters): 226 226 232 227 225 228 225 228 229
but instead of 10 numbers/measurements, the post presents only 9.
This post, word in word and number in number, was just submitted once some time ago with the same error, and one of the tutors noticed it.
Now it came with the same error . . .
Why do you submit DEFECTIVE posts, and repeat the same error SEVERAL times ?
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